Logical Reasoning

PT126 · S4 · Q23 Physics professor: Some scientists claim

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Physics professor: Some scientists claim that superheated plasma in which electrical resistance fails is a factor in causing so-called “ball lightning. ” If this were so, then such lightning would emit intense light and, since plasma has gaslike properties, would rise in the air.

Conclusion

Superheated plasma with failed electrical resistance is never a factor in causing ball lightning.

Evidence

If superheated plasma with failed electrical resistance were a factor in causing ball lightning, then that lightning would emit intense light and would rise in the air.

But the instances of ball lightning I've seen were of low intensity and floated horizontally before vanishing.

Evaluate

This stimulus is written to make our brains turn into applesauce. We need to chunk down "superheated plasma in which electrical resistance fails" into one idea, X.

We need to also recognize the rebuttal structure of the argument. Authors often refute a certain claim by saying, .

When authors say something like, "If this were true ...", we call it Implications of Logic. The right side of a conditional is the implication of the left side. Authors go on to tell us that the implication is untrue / absurd / unacceptable, in order to rule out the original trigger idea, via Contrapositive Logic,

The argument looks like this:

Some scientists claim X is a factor in causing Y. If X were a factor is causing Y, then A and B would follow. But when I saw Y, there was ~A and ~B. Thus, X is never a factor in causing Y.

The contrapositive logic checks out. The real gap between the evidence and the conclusion is that the evidence is about "the instances of ball lightning that I observed", whereas the conclusion is about "never a factor, in any instance".

We are logically sure that that X was not a factor in the ball lightning that the author observed (because neither of the symptoms of such an occurrence, intense light and rising in the air, were present.

But we can't be logically sure that X is never a factor in causing ball lightning, because we don't know whether the instances of ball lightning the author observed are representative of all cases of ball lightning.

Goal

We need to get from

23.

The physics professor's conclusion follows logically if which one of the following is assumed?

  1. Superheated plasma in which electrical

    Out of Scope

    Out of Scope: other than ball lightning This argument is only about ball lightning.

    11% picked this

  2. The phenomena observed by the

    Too Weak

    This strengthens the argument somewhat, to know that the professor's accounts can be corroborated by other people. But that doesn't "seal the deal" and guarantee the incredibly strong wording of the conclusion that "X is never a factor in causing ball lightning."

    2% picked this

  3. Ball lightning can occur as

    Weakens

    If ball lightning has lots of different origins stories, then there's no reason to think that the instances the physics professor observed show the full range of possibility. The author is boldly saying X is never a factor, so she's really trusting that what she saw speaks for all cases. This answer makes it sound like different cases of ball lightning could be unfair to compare.

    11% picked this

  4. Superheating of gaslike substances causes

    Unrelated to Goal

    This is pulling together language from within the premises so that we see some sort of Linking answer and consider it. The argument said that superheating plasma (a gaslike substance), were it to spark some ball lightning, would cause that ball lightning to emit intense light. We already knew superheating gaslike substances can lead to bright light being emitted, so this answer is only pumping up the strength of what we already knew. But it has nothing to do with helping us know for sure that "if X wasn't a factor in the instances the professor observed, then X is never a factor in ball lightning." All this answer would be doing is adding more corroboration for the professor's story that the instances of ball lightning she observed are enough for us to say something would never be true about ball lightning.

    10% picked this

  5. Correct

    All types of ball lightning

    Why this is right

    We know that when superheated plasma with failed electrical resistance (X) causes ball lightning, there would be intense light and rising in the air. The instances the professor observed were not-bright light and not-rising in the air. So we know that X was not a factor in those instances of ball lightning. This answer allows us to generalize from those instances to all instances, by giving us a powerful idea that every case of ball lightning has the same causal factor. Thus, if X wasn't a causal factor in the instances the professor observed, then X is never a causal factor.

    Skill tested: Sufficient Assumption · how this choice captures the argument's function is the move to repeat next time.

    66% picked this

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